* Futures down: Dow 39 pts, S&P 4.25 pts, Nasdaq 5.25 pts
By Yashaswini Swamynathan
March 29 (Reuters) - U.S. stocks index futures were slightly lower on Tuesday as investors await Federal Reserve Chair Janet Yellen's speech for clues about when the central bank may raise interest rates.
* Yellen, who is due to speak before the Economic Club of New York at 12:20 p.m. ET (1620 GMT), will make her first remarks since the Fed's meeting in March.
* The central bank has said it will depend on economic data before it makes a decision on rates, but several policymakers have voiced support for more than one increase this year.
* Investors will keep a close eye on Yellen's remarks as they look for fresh drivers that could push stocks higher. The S&P 500 is back in the red for the year after a five-week rally fizzled out.
* U.S. stocks ended flat on Monday on low volumes after data pointing to a sluggish economic recovery reduced concerns of rate hikes and a dip in oil prices pushed down energy stocks.
* Crude oil fell about 2 percent as analysts forecast that U.S. stockpiles would touch record levels.
* The Conference Board's consumer confidence index, due to be released at 10:00 a.m. ET, is expected to have risen to 94 in March from 92.2 in February.
* Among other Fed officials speaking on Tuesday is New York Fed President William Dudley.
* Shares of Lennar were up 2 percent at $47.68 premarket after the homebuilder reported results.
Futures snapshot at 6:56 a.m. ET:
* Dow e-minis were down 39 points, or 0.22 percent, with 19,254 contracts changing hands.
* S&P 500 e-minis were down 4 points, or 0.2 percent, with 140,511 contracts traded.
* Nasdaq 100 e-minis were down 5.25 points, or 0.12 percent, on volume of 17,884 contracts. (Reporting by Yashaswini Swamynathan and Abhiram Nandakumar in Bengaluru; Editing by Saumyadeb Chakrabarty)